1. Field of the Invention
The present invention relates to a method of fabricating memory devices and, more particularly, to a method of fabricating memory devices, which method can prevent (a) a hard mask layer for a bit line from being bent, (b) a short between bit lines and lower electrodes, and (c) formation of bridges between storage node contact (SNC) plugs.
2. Brief Description of Related Technology
As the design rule of DRAM devices decreases, a method of forming a SNC employing a line-shaped etch mask emerges in order to widen an area where a lower region is opened.
The critical dimension (CD) of a semiconductor device pattern is being reduced as semiconductor devices become more highly integrated. In a conventional process of forming the line-shaped etch mask, however it is difficult to reduce the height of the line-shaped etch mask having a high height (that is, a hard mask layer for a bit line).
In particular, a hard mask layer (for the bit line) having a high aspect ratio has the following problems. First, the hard mask layer has a height of about 2500 angstrom (Å). Thus, at the time of an etch process of forming the line-shaped etch mask, the hard mask layer for the bit line is bent due to a high aspect ratio.
Second, the line-shaped etch mask does not properly serve as a mask due to the bent line-shaped etch mask when an excessive etch process is carried out in an etch process of forming lower electrodes, so that the bit line is partially exposed. This results in a short phenomenon between a lower electrode and a bit line. If misalignment occurs in this situation, then the short phenomenon between the lower electrode and the bit line becomes more profound.
Third, when conductive and barrier metal layers for a bit line are etched by employing a hard mask pattern for the line-shaped bit line, an upper region of the hard mask pattern is lost excessively and resultantly has a positive profile. If a process of forming spacers on the sidewalls of the hard mask pattern and the bit line is performed, then the spacers are also formed on the upper region of the hard mask pattern having the positive profile, resulting in bridges between SNC plugs. Consequently, reliability of the device becomes very vulnerable.